I. Field of the Invention
The present invention relates generally to an assembly for delivering fluids to a desired location within the body; and more particularly, relates to a catheter or similar medical device used to infuse pharmaceutical agents or other fluids into the body so that the velocity of the stream of injected fluid at or near the fluid ejection or delivery site is reduced so as to avoid unintended injury or trauma to body tissues from the fluid ejection.
II. Discussion of the Prior Art
Physicians today often use a microbore catheter placed to extend to a selected location within a patient's body for both the administration and receipt of fluids. Microbore catheters are catheters which generally have a very small internal diameter along their lengths. Microbore catheters have a unique advantage over other conventional catheters in that they tend to be more slender, making them easier to use. Ease of use is particularly advantageous when catheters are utilized for various neurological applications. For instance, placement of a parenchymal catheter near or within the brain for all practical purposes requires that a relatively small device like a microbore catheter be used to avoid unintended injury to the brain. (Use of a parenchymal catheter generally involves the insertion of a catheter within the brain to dispense pharmaceutical agents at a specific desired location; the locations include the ventricular spaces of the brain.)
It is also generally advantageous for catheters to have a relatively smaller internal diameter since a smaller internal diameter results in the catheter having reduced dead volume. Dead volume is equivalent to the total carrying capacity of the catheter at any given time. The larger the carrying capacity the more fluid must flow into the catheter before being available for delivery to a site within the patient's body. Thus, minimizing dead volume is important in situations where very low flows are required to limit delay in delivery of the fluid to the desired site and in limiting bolusing of small dosages of drugs.
Using conventional microbore catheters to deliver pharmaceutical agents or other fluids to a desired location within the body, however, has a significant drawback. While the use of small size catheters can be an advantage on one hand, the use of microbore catheters also can be disadvantageous precisely because of their small size. More specifically, the small inner diameter of the microbore catheter causes the fluid to be delivered at a relatively high velocity, particularly when the fluid is being supplied to the catheter by manual means, such as a syringe, or by a drug infusion pump (external or implantable) programmed to provide bolus injections. The high velocity achieved by shooting the fluid through the narrow lumen of the catheter can create a harmful cutting or otherwise traumatizing injury to tissues adjacent the microbore catheter at the fluid ejection site.